(a) Field of the Invention
The present invention relates to an insect repellent isolated from Foeniculum vulgare fruit, and more particularly, to an insect repellent comprising one or more compounds selected from the group consisting of fennel oil which is isolated from Foeniculum vulgare fruit, (+)-fenchone and E-9-octadecenoic acid.
(b) Description of the Related Art
There are about 3000 different species of mosquitoes throughout the world and among said mosquitoes, about 500 species of Aedes, about 300 species of Culex, and about 350 species of Anpheles cause hygienic human suffering (Harwood, R. F. and M. T. James. 1979. Entomology in Human and Animal Health. Macmillan). In Korea, about 51 species of mosquitoes are reported with 20 species of Aedes, 18 species of Culex, and 7 species of Anpheles (Hyo Suk You, 1994. Chack List of Insecta from Korea. Kon-Kuk University Press).
Mosquitoes not only bite humans and animals, but also transmit mosquito-borne diseases such as malaria, encephalitis, yellow fever, and dengue and subsequently cause a lot of human death. Currently, two-thirds of the world's population is exposed to mosquito-borne diseases.
Also, mosquitoes are harmful insects which cause great suffering directly or indirectly through stress caused by bites, such as sleeping interference and restriction of field work (Kettle, D. S. 1991. Medical and Veterinary Entomology. Wiley Interscience Publication. New York).
Among mosquitoes known in Korea, Anopheles sinensis cause malaria, Inland brugian filariasis and Aedes togoi cause filariasis in the south coast region, Culex tritaeniorhynchus cause Japanese encephalitis and Culex pipiens pallens and Culex pipiens molestus cause trouble with bloodsucking in apartment regions. Thus it is necessary to control these insect pests (Han II Lee. 1998. Medical Entomology (4th) Komoonsa, Seoul, 340 pp).
Control of the mosquito population was primarily dependent upon chemical control by application of insecticides. However, use of synthetic organic insecticides has caused harmful side effects such as drug-resistance, toxicity to nontarget organisms, and long-term contamination of the environment (Georghiou, G. P. and Saito, T. 1983. Pest Resistance to Pesticides. Plenum Press, New York and London; National Research Council. 1986. Pesticide Resistance: Strategies and Tactics for Management. National Academy Press, Washington, D.C.; Brown, A. W. A. 1978. Ecology of Pesticides. Academic Press, New York.). Therefore, it is necessary to develop new types of selective alternatives for use as insecticides and methods of controlling insect pests which are non-toxic to humans and the environment while still protecting people from mosquitoes.
Repellents made from natural compounds that inhibit insects' responses are highlighted as new types of insect control agents, and such repellents can prevent insect-borne diseases without harmful side effects such as environmental contamination.
However, because repellents are directly applied to people, they must meet many requirements. Repellents must be nontoxic to humans, long-lasting, nonirritating, inoffensive in odor, chemically stable, effective on the whole body even when applied to only a part of the skin, and so on.
Recently, as the study of plant extracts and plant-derived materials has progressed, secondary metabolites of plants such as terpenoids, phenolics, alkaloids have been issued because they are nontoxic to the body, simple in treatment method, and active against a limited number of species including specific target insects. Therefore, much efforts has been focused on plant materials for potentially useful prodeucts as commercial insecticides or as lead compounds. (Jacobson, M. and Crosby, D. G. 1971. Naturally Occurring Insecticides. Marcel Decker, New York; Elliot, M. 1977. Synthetic pyrethroids, pp. 1–28, in M. Eliott (ed.). Synthetic Pyrethroids. ACS Symp. No. 42, Amer. Chem. Soc., San Francisco, Calif.; Hedin, P. A. 1982. J. Agric. Food Chem. 30: 201–215; Arnason, J. T., Philogene, B. J., and Morand, P. 1989. ACS Symp. Ser. No. 387, Amer. Chem. Soc., Washington, D.C., 1989; Isman, M. B. 1995. Rev. Pestic. Toxicol. 3:1–20.) The plants containing repelling activity components against mosquitoes have been reported, like as Lantana camara, Artemisia vulgaris, Eucalyptus species, and oil from the Neem tree (Dua, V. K., N. C. Gupta, A. C. Pandey and V. P. Sharma. 1996. J. Am. Mosq. Control Assoc. 12: 406–408; Sharma, V. P. and M. A. Ansari. 1994. J. Med. Entomol. 31: 505–50).
In China, the Eucalyptus-derived p-menthan-3,8-diol (PMD) repellent is made from waste distillate after extraction of oil from Lemon Eucalyptus. PMD is less effective than DEET (N,N-diethyl-m-toluamide), but it is effective on Anopheles and it is also applied to ticks, flies, and nidges. Also, because PMD does not react with plastic and synthetic fibers as does DEET, it can be applied to such goods and it is very nontoxic (Oral administration test of rat LD50 2,408 mg/kg, epidermal test of rat LD50>2,000 mg/kg: Trigg, J. K. 1996. J. Am. Mosq. Control Assoc. 12: 243–246).
DEET, the most common mosquito repellent, has been extensively used. In the United States, it is estimated that more than 30% of the population use DEET-containing insect repellent products during the insect-biting seasons and over 30 million packages of DEET products are sold annually (1994). DEET is not only effective on a variety of species of harmful insects such as flies, lice, fleas and ticks, but it is also used on nidges and to protect domestic animals.
On the other hand, Malaria in Korea, which had completely disappeared in the 1970's, has been once again seen since 1993, and 3,330 patients contracted the disease between then and September 1998. As of 1999, the number of Malaria infected patients had not been reduced, but on the contrary, the infection rate of non-official civilians has gradually increased and the malarial region has spread from the neighborhood of the demilitarized zone to the whole northern part of Kyunggido. Recently, the number of cases of Japanese Encephalitis has been reduced, but that is small consolation.
In America, mosquito-borne diseases like Encephalitis and Yellow Fever were rampant in the 1990's, and vector-borne diseases such as West Nile Encephalitis which were not previously known have spread.
Also, due to a rise in temperature and change of the environment due to global warming, the appearance of mosquitoes and subsequent bloodsucking activity is increasing. Thus anxiety about damage by mosquitoes is also increasing.
In this situation, although control of mosquitoes through the known synthetic insecticides and use of repellents that protect from mosquito-borne diseases is increasing, little progress has been made in the development of repellents that can overcome the problems of the currently used repellents.
The typical synthetic repellent DEET has several problems. For example, it has an unpleasant odor, it causes irritation to the skin, and it tends to damage glasses and watch straps as reactions occur with some plastics and rubbers. In addition, due to the most problematic issue, which is rapid and strong penetration of the skin, it is restricted in use. In 1982, it was confirmed that the skin penetration ratio of DEET was 30% after 1 hour under the condition whereby the skin was treated with 300 ug/cm2 DEET, and the ratio was 36% after 12 hours. So, the use of DEET has been restricted on children, hypotensive patients, and people with sensitive skin, and adults also cannot cover more than 30% of the surface area of their body.
Therefore, a novel material is required that can reduce the use of DEET and that includes repelling effects. Although detection of non-toxic substitute plant materials is in progress, the development of repellents meeting the complicated requirements is still lacking.